The Landmark London, a five-star Grande Dame hotel in Marylebone, has been a feature in the capital for more than 100 years.
It features an eight-storey glass atrium; 300 rooms, including 51 suites; a spa and health club; banqueting suites; a ballroom; and four drinking and dining destinations.
The agency will manage comms for all these elements, implementing a strategic PR campaign.
It will generate reviews and endorsement, profile key spokespeople within the business and host media and influencer stays.
Liam Keogh, one of the agency's founding directors, said: "Palm's campaign across consumer and trade media will aim to raise awareness of the hotel and all its amenities, while celebrating its significant 120th anniversary."